The definition of lot size makes it easier for you to select an appropriate alternate, depending on how much of the part needs be produced for the moment.
When the part is manufacturing, it is possible to define which routing/structure alternate will be automatically selected when a part should be produced, depending on the lot size that should be produced via the Minimum Lot Size Based Qty field in the Routing page or the Minimum Lot Size Based Qty field in the Product Structure/Recipe Structure page. When a shop order or shop order requisition is created, the correct alternate should be automatically selected based on the actual lot size.
MRP, PMRP, Master Scheduling, DOP, CRP, Multilevel Availability Check and Order Availability also uses the lot size rule in order to pick the correct routing/structure alternate. This affects the calculation of planned order/operation start dates and the demand of components. If lot size based is used and a shop order is created or changed with no hits for the lot size, the * alternate will automatically be selected. (Shop order lot size is lower than the smallest minimum quantity that is defined for lot size).
When the lot size on the shop order is changed and the new lot size is not corresponding to the alternate on the shop order, a message will be displayed. It is possible to right-click and click Update Routing Alternate for Lot Size or Update Structure Alternate for Lot Size to automatically change to the correct alternate if the shop order is in the Planned or Released status.
On the Unit Cost per Alternate page it is possible to analyze the unit cost per lot size and alternate. If there are breakpoints between graphs, they show when it is most economical to change production from one alternate to another. The Part Routing Cost page can be used to simulate the routing cost for different routing alternates and lot sizes in the Tentative, Planned and Buildable statuses. Only the last simulated result for each revision/alternate will be saved.
The routing lot size cannot be used for CTO parts as well as when the routing effectivity type is Serial. In this instance, the unit cost per alternate will be available but the graph will not consider any routing rules. The standard cost calculation will always use the * alternate, independent of which alternate is valid for the standard lot size.